Holddown device for screen frames



Sept. 29, 1953 Filed Feb. 14, 1950 D. CRAMPTON 2,653,714-

uownowu DEVICE FOR SCREEN FRAMES 3 Sheets-Sheet 2 calmly."

E? H M INVENTOR. 09 BY Sept. 29, 1953 CRAMPTQN 2,653,714

, HOLDDOWN DEVICE FOR SCREEN FRAMES Filed Feb. 14, 195of s Sheets-Sheet s 82 k m 88 29 26 as 92 9080 a4 p/ Q 72 min "IIIIIIIIIIIIIIIIIIIIIIIII can be secured and vibration will be minimized.

At spaced intervals along each of the main longitudinal side channels 20 of the sifter frame the reduced upper ends 29 of depending tie rods 36 extend upwardly through the flanges of the beam 26 and are secured to nuts 32 supported on the upper flange of this beam with the shoulders separating the reduced ends 29 and lower portions 3i of the rods 30 in contact with the lower flanges of the beams 20. The lower ends of the tie rods 39 extend through the side angle bars 34 of a supporting platform frame 36. The frame 35 comprises the side angle bars 34, the end transverse angle bars 38 which connect the ends of the bars 34, and intermediate transverse angle bars 46 which connect the side angle bars 34 at places directly below the transverse channel beams 22 of the main frame of the sifter. The platform frame 36 and the platform 42 on the bottom side thereof are supported by nuts 44 at the lower ends of the vertical tie rods 30.

The platform 42, as shown in the drawings, carries at each end intermediate the reeds 24 and the channel beams 20 two stacks of screen frames 46. The inner construction of the screens in frames 46 is not a feature of the present invention. If desired, the screens may be like those shown and described in the copending application above referred to or they may be of any other construction suitable to sift, bolt, separate, screen, or grade th material being handled into different sizes. Holes in the bottom of the platform 42 provide communication with outlet spouts 48 through which the sifted or graded material is withdrawn.

Three of the corners of each stack of screen frames 46 are embraced by vertical angle bars 50, 52, and 54. The vertical angle bars 50 fit into the corresponding corners between the longitudinal channel beams 20 and the transverse channel beams 22 of the main frame of the sifter. The vertical angle bars 52 have their lower ends inside the transverse angle bar 40 of the platform frame and intermediate their lengths are preferably attached as by welding to the transverse channel beams 22 of the main sifter frame. At their upper ends the bars 52 are preferably attached to the transverse angle bars 23 which lie above and parallel to the beams 22 and bars 40 and which are connected at their ends by the longitudinal members 25. The bars 52 embrace, respectively the adjacent inside corners of the stacks of screen frames 46.

At the outside corners of the stacks of frames 45 which are adjacent to the corners of the platform 4?. vertical angle bars 54 are provided, the bars 54 being arranged inside of the main longitudinal channel beams 20 and the platform frame angle bars 34 and 38. The angle bars 50, 52. and 54 may be secured in position by any suitable means. If desired the vertical bars 52 may be permanently fixed in position, as by bolting, welding, or rivetting, and the bars 50 can be ad.. .iustably moved toward these bars 52 to clamp the screen frames therebetween by the clamping means shown in the application above referred to.

A clamping plate 56 is pivotally mounted at each end of the platform 42. The member 56 c mpri es a flat face plate 58 which is provided adjacent its lower end with a par of outwardly extending lugs 68 which are secured to a mounting block 62 by the hinge pin 64 and nut 66. The blcc'ts 62 are preferably welded to the bars 38 of the platform frame 36. The face plate 56 has integrally attached thereto on the rear side thereof a pair of spaced inwardly extending flanges 68.. The clamping member 56 is adapted to be swung around a horizintal axis on hinge pin 64. When in normal vertical position the member 56 has the face plate 58 overlapping and flush against the sides of the adjacent stacks of screen frames 46 with the inwardly extending flanges 68 serving to prevent sidewise displacement of the frame 46.

In efiect, the clamping member 56 provides a pair of angle bars mounted on a single pivoted plate. The clamping member 56 is provided with a handle Hi and is held in vertical position by a plurality of wing nuts 12 which are secured on the threaded ends of the tie rods 14. The tie rods 14 are secured at their inner ends to a vertical plate 16 which extends transversely substantially the full width of the sifter and is scoured to the transverse channel beam 22 and transverse angle bars 23 and 46 by welding or other suitable means. The tie rods 14 pass through the vertical plate 16 and are held thereto by nuts 18 screwed on the threaded ends of the tie rods on each side of the plate 16. Tightening of the wing nuts 12 on the tie rods 14 resuits in the face plate 56 exerting pressure on the corners of the screen frames 46 and drawing them into close engagement with the vertical angle bars 52. Since the sifter is subject to rapid gyratory motion it is essential that the screen frames 453 be firmly clamped in alignment. Clamping of the adjacent sides of the two stacks of frames carried at each end of the sifter is obtained by the clamping members 56 as above described.

To each end of each of the main longitudinal side beams 20 of the main frame of the sifter there is secured a clamping plate 89 which is L-shaped in horizontal section. Each of the L- shaped clamping plates is provided with a pair of vertically spaced, outwardly extending ears 82 which are secured for pivotal movement to the outwardly extending flanges of the adja cent channel beam 20 by means such as a pivot pin or bolt 84. The clamping plates 80 can thus be swung to embrace the corners of the vertical angle bars 54.

Each clamping plate 60 is provided with a lug 86 which projects outwardly from the corresponding end of the sifter. Each of the lugs 80 is provided with an upwardly directed slot 88, the slots 88 in the two clamping plates 80 at each end of the sifter being in horizontal alignment and in the same vertical plane. A rod 20 threaded at both ends for the mounting of hand wheels 92 is received within the slots 88 with the hand wheels on the outer sides of the lugs 86. When the hand wheels 92 are turned on the screw threaded ends of the rod the hubs 93 of said wheels are brought to bear against the lugs 86 and in pulling the lugs together cause the vertical angle bars 54 embraced by the clamping plates 60 to press against the corners of the screen frames 46 and thus to clamp the stack of frames securely between the vertical angle bars.

Although the screen frames 46 are clamped between the member 56 and the angle bars 56, 52 and 54 to prevent horizontal shifting with respect to platform 42, it is also necessary to hold the screen frames firmly down against the platform frame 36. By the present invention there is provided mechanism for securely clamping the screen frames 46 downwardly against the platform frame 36 by means attached to the top frame 96 with which each stack of screen frames is equipped.

Each of the top frames 9,61 equipped with an inlet spout. as, in the top. th re f t rough. which the materials tobe sifted or screened are. ad:- mitted to the rectangular header I08. which is interposed between the top screen fram 4. in each stack and the top frame 9,6 and preferably projects upwardly above the tops of the angle bars 50 52 and 5d and the clamping plates 58 The headers we provide receptacles within which the material to. be sifted or screened. collects. and from which the material is fed to the series; of Screens below. If desired, the headers. Itil and top frames 96. can be attached or made integral to, constitute a unitary structure. On opposite sides of each of the top frames 96 adjacent the corners, thereof there are provided pins 9,2 which extend horizontally outwardly therefrom with the pins I02 on one side of each cover projecting over side beams 20. Pivotally mounted on the. pins I02. and depending therefrom are, elongated drawbars or tension members Iild and lil't'a, these drawbars being of identical construction except that the drawbars Ifi ia are of somewhat greater length than the drawbars IM so as to avoid interference.

At its lower end each of these drawbars is pivotally secured to a pivot pin I86, projecting horizontally from a nut I98 these nuts form: mg independently floating members. Pivotally mounted on these pins I05 and depending there; from are another set of elongated tension members or drawbars I I0, IIIla, these drawbars being of identical construction except that the drawbars IIGa are of shorter length and are associated with the longer drawbars "Ma. The lower ends of the lower drawbars IIIJ, Iita are secured to pivots II2 projecting horizontally from angle bars II which are suitably secured to the upper face of the platform 42. It will be noted that the pivots IIZ are located outside of the downwardly projected centerlines of the tension members or bars IN.

The pair of nuts 38 at each side of each of the stacks 46 have axially alined, reversely threaded bores and are connected by a horizontally disposed draw screw H6, which is threaded substantially throughout its len th with the threads on one end thereof being directed oppositely from the threads on the other end. The outwardly facing ends of the draw screws I I6 are provided with squared portions I I8, which are adapted to be enga ed by a key or socket wrench.

In order to provide access to the. Squared end portion H8 of the draw screws H5 arranged between the stacks it of sifter frames, an access opening In is provided in the clamping plate 55.

It is not essential that the members lit, IIlic be tension members since these members can be under compression as illustrated in Fig 8. Thus in this figure pivotally mounted on the pins I82 are elongated drawbars I24, the lower end of each of which, as with the drawbars I84 in the form of the invention shown in Figs. 147, being pivotally secured to a pivot pin I26 projecting horizontally from a nut I28. Pivotaily mounted on these pins I26 and extending Lip-.1 wardly therefrom are another set of links in the form of compression members or bars Ifid, The opposite ends of these compression members or bars I3t at each side of each stack are secured to a common pivot pin I32 which is located be tween the drawbars or tension members I24. Each of these pivots projects from the side of 6 an L-shane b acket ecu ed; to the up er ec of. he n attorm 42.-

Th pair r u s I-Z lat ea h si e o the, sta ks In the following description, it. will bev assumed h t the o e sof. each s a k 4 0i screens. ha been released from the angle bars 5.0, 52 and b T e se ea h toc fr m thes n e ar the. hand W els 9.2 n. the, rod so ar u screwed suiiiciently' to. permit this rod to. be raised from the s10ts88 inthe lugs; I36,v The rod 90, is then removed and the, clamping platesswung outward? ly and backon the pivot pins or bolts 8,4,. The an le ars 54 a e the r moved- Th ang bars 50 are then rerngved from inward clamping engagement with the stack of screens. this clamping mechanism not being Shown. The wing nuts I2 are then unscrewed and the clamp: ing plate swung outwardly and downwardly; on the hinge pin 64,, The sifter is then in condi: tion for raising the top, frames 46, through the mechanism embodying the present invention, it being understood that the reverse of the above operat o i per med o rec amp he tacks 4S laterally by the angle bars 50, 52, 54 and 55.

t wi l be s hat he inven on s ess nt a ly embodied in the holddown for the top frames 46 and comprises a pair of tension members, such as the drawbars IE4 or I24, at the opposite sides oi each stack 46 of screen frames and connected at their upper ends to, the corners of the top. frame of the stack, together with means @011? straining the lower ends of the pair of tension members to follow a, downward path on being drawn together, in combination with a means, such as the nuts H8 or I 28 and draw screws H5 or I36 for drawing the lower ends of these tens on members together. I the o m o th invention shown in Figs. 1:7, the guides for so constrainin e nsion membe IM- to f l ow a downward path on bein drawn together are the tension links or bars III) which, by virtue f their iv s H2 b in lo ated outs f he downward proj ct ons f h c n rlines f the tension bars I04, have their upper ends arranged t w ng n a nwed pat on. be draw to ethe and her by ef e t a or esp nd g wnward mo em nt o th pper ensi ars 1 In the f rm o he invention shown n Fi 8. h ui es for so cons rain n t ten si mem e I2 to fol o a down ard pa on being drawn together are the compression bars or m mb rs 30 hich b v rtu of t i com on pivo 32 be ng oca ed. betw en the en: n r I24. h e their lower nds a an ed to swi in a downward at n be ng d awn o ther and ther y f ect a corr ndin wnwa d mo ement of he ensi a I 4.

It i l a icularly be no ed hat t e h lo o n f t p esent inve tion ser es to eq alize he. amping pre su es on e corners oi the by irtue of the fl atin conn cti n of e I98 through the bars IIQ IIjtic with the bottom support 35 of the sifter. Thus assuming that, say. th upper igh hand co ner of the stae of creens frames s viewed n F g. 1 is highe th n he up er le t hand orner, on t rning he c ew havin ts t ier. fla e,

7 I I6 the nut I08 at the left would be drawn further toward the center of the stack than the nut I08 on the right and the screw H6, in the final position, would be at an angle to the horizontal, inclining downwardly toward its headed end. By virtue of this distortion of the linkage due to its floating anchorage, the holddown would apply the same downward pressure at the one corner as the other in spite of the fact that one corner is higher than the other, as assumed. Accordingly the holddown applies equalized clamping pressures to the corners of the top frames of the stack or stacks of screen frames.

Accordingly, in the form of the invention shown. in Figs. 1-7, turning any draw screw II6 to draw its pair of draw nuts I08 together causes the upper ends of the corresponding pair of tension members or links I I U to swing toward each other and downwardly about their pivots I I2. This causes a corresponding downward movement of the upper tension members or bars I64 thereby to draw the top frame 96 firmly down upon the corresponding stack 46 of screen frames. Conversely, when it is desired to lift the top frames 96, the draw screws II6 are turned to spread the nuts I08 thereby to swing the upper ends of the tension bars or members I I6 about the pivots I I2 upwardly and away from each other. This causes a corresponding upward movement of the upper tension members or bars I04 thereby to lift the.- top frames 66 and provide ready access to individual screen frames in the stacks 65 thereunder.

In the form of the invention shown in Fig. 8.

turning any draw screw I36 to draw its pair of draw nuts I28 together causes the upper ends of the corresponding pair of compression members or links I36 to swing toward each other and downwardly about their pivot I32. This causes a corresponding downward movement of the upper tension members or bars I24 thereby to draw the top frame 96 firmly down upon the corresponding stack 46 of screen frames. Conversely, when it is desired to lift the top frames 96, the draw screws I36 are turned to spread the nuts I38 thereby to swing the upper ends of the compression bars I36 about the common pivots I32 upwardly and away from each other. This causes a corresponding upward movement of the tension members or bars I24 thereby to lift the top frames 96 and provide ready access to the individual screen frames in the stacks 46 thereunder.

In the foregoing specification, there has been described one embodiment of the present invention as applied to a sieve of the general type shown and described in the said copending application, Serial No. 562,753. It will be understood, however, that the invention is capable of application to other sifter constructions and that modification to adapt the invention for such use is within the spirit of the present invention. It will be further understood that numerous modifications of the details of construction shown and described herein may be made without departing from the spirit of the invention. Accordingly, it is desired that the invention should not be limited by the foregoing description and the accompanying drawings, but is to be accorded the full range of equivalents comprehended by the accompanying claims.

I claim:

1. An equalizing holddown for a stack of screen frames mounted on a support and said stack having a top frame, comprising at least one pair of downwardly converging elongated tension members severally connected at their upper ends to the corners of said top frame to swing adjacent to and parallel with the side of said stack bounded by said corners and the lower end of each of said tension members being disposed closer to said support than to said top frame, a pair of independently floating members pivotally secured severally to the lower end of each of said tension members, a guide structure secured to said support below said pair of tension members, means movably connecting each of said independently floating members with said guide structure and constraining said independently floating members to move vertically relative to said support in response to movement thereof toward and from each other but permitting movement thereof relative to said support independently of each other, and a floating, manually operable screw means connecting said pair of independently floating members and arranged to positively move said independently floating members toward and from each other thereby to raise and lower said top frame and to apply equalized downward pressure at said corners of said top frame against said stack of screen frames.

2. An equalizing holddown for a stack of screen frames mounted on a support and said stack having a top frame, comprising at least one pair of downwardly converging elongated tension members severally connected at their upper ends to the corners of said top frame to swing adjacent to and parallel with the side of said stack bounded by said corners and the lower end of each of said tension members being disposed closer to said support than to said top frame, a pair of nuts movably secured severally to the lower end of each of said tension members to move about horizontal axes perpendicular to said side of said stack, each of said nuts being provided with a generally horizontal threaded bore arranged transversely of its said axis, means movably connecting each of said nuts with said guide structure and constraining said nuts to move vertically relative to said support in response to movement thereof toward and from each other but permitting movement thereof relative to said support independently of each other, and a floating, manually operable generally horizontal screv. having its opposite ends screwed into said pair of nuts and formed to move said nuts horizontally toward and from each other thereby to raise and lower said top frame and to apply equalized downward pressure at said corners of said top frame against said stack of screen frames.

3. An equalizing holddown for two closely spaced parallel stacks of rectangular screen frames mounted on a common support and each of said stacks having a top frame, comprising a tension bar connected at its upper end to each of the four corners of each of said too frames to swlng parallel with the space between said stacks and the lower end of each of said tension bars being disposed closer to said support than to said top frame, two pairs of said tension bars being arranged in said space with each pair close to the side of a corresponding stack and the other two pairs being each arranged close to the face of the corresponding stack opposite said space, a nut movably secured to the lower end of each of said tension bars, a plurality of guides mounted on said support severally below and projecting nuts and constraining each pair of saidnuts to move both upwardly and downwardly relative to said support independently of one another in response to horizontal movement of each pair of nuts toward and from each other, and four manually operable generally horizontal screw members arranged parallel with the space between said stacks and each having opposite ends operatively connected with the corresponding pair of nuts to move said pair of nuts horizontally toward and from each other thereby to raise and lower each top frame relative to its stack and to apply equalized downward pressures at said corners of said top frames against said stacks of screen frames.

4. An equalizing holddown for two closely spaced parallel stacks of rectangular screen frames mounted on a common support and each of said stacks having a top frame, comprising a tension bar connected at its upper end to each of the four corners of each of said top frames to swing parallel with the space between said stacks and the lower end of each of said tension bars being disposed closer to said support than to said top frame, two pairs of said tension bars being arranged in said space with each pair close to the side of a corresponding stack and the other two pairs being each arranged close to the face of the corresponding stack opposite said space, a nut removably secured to the lower end of each of said tension bars, eight bars each associated with and being substantially shorter than a companion tension bar, a pivot connection between one end of each of said shorter bars and a companion nut, a second pivot connection between the other end of each of said shorter bars and said support and located in vertically spaced relation to the companion first pivot connection, each pair of said second ivotal connections being located intermediate the companion pair of said first pivot connections whereby each pair of said nuts is constrained to move both upwardly and downwardly relative to said support independently of one another in response to horizontal movement of each pair of said nuts toward and from each other, and four manually operable generally horizontal screw members arranged parallel with the space between said stacks and each having opposite ends operatively connected with the corresponding pair of nuts to move said pair of threaded nuts horizontally toward and from each other thereby to raise and lower each top frame relative to its stack and to apply equalized downward pressures at said corners of said top frames against said stacks of screen frames.

5. A structure as set forth in claim 4 wherein said second pivot connection is arranged below said companion first pivot connection.

6. A structure as set forth in claim 4 wherein said second pivot connection is arranged above said companion first pivot connection.

7. An equalizing holddown for the adjacent corners of two closely spaced parallel stacks of rectangular screen frames mounted on a common support and each of said stacks having a top frame, comprising a tension bar connected at its upper end to each of the adjacent corners of said to frames to swing parallel with the space between said stacks and the lower end of each of said tension bars being disposed closer to said support than to said top frames; two pairs of said tension bars being thereby arranged in said space with each pair close to the side of a corresponding stack, a nut movably secured to the lower end of each of said tension bars, at least one guide structure mounted in said space on said support and projecting upwardly toward said pairs of tension bars, means operatively connecting said guide structure with said pairs of nuts and constraining each pair of said nuts to move both upwardly and downwardly relative to said support independently of one another in response to horizontal movement of each pair of said nuts toward and from each other, and a pair of manually operable generally horizontal screw members arranged in and parallel with the space between said stacks and each having opposite ends operatively connected with the corresponding pair of nuts to move said pair of nuts horizontally toward and from each other thereby to raise and lower the corresponding top frame relative to its stack and to apply equalized downward pressures at said corners of said top frames against said stacks of screen frames.

DAVID CRAMP'ION.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 167,297 Buhlmann Aug. 31, 1875 419,884 Richards Jan. 21, 1890 1,403,589 Cinquini Jan. 17, 1922 1,492,326 Kennedy Apr. 29, 1924 1,497,708 Anderson June 17, 1924 1,750,521 Judd Mar. 11, 1930 1,973,308 Geistlinger Sept. 11, 1934 2,516,256 Robinson July 25, 1950 FOREIGN PATENTS Number Country Date 7,372 Great Britain of 1909 187,619 Germany June 29, 1907 197,050 Germany Feb. 5, 1907 353,902 Germany May 29, 1922 624,465 Germany Mar. 12, 1935 OTHER REFERENCES American Miller, April 1949, pages 64, 209-319. 

